建议：先实现同一个半球上的计算,正确运行之后再拓展到两个半球.

#include
#include
const double R=6378.1370;
const double pi=3.141592654;
double chord_len(double a,double b);
double arc_len(double a,double b);
double chord_len(double a,double b)
{
double x,rad;
/*printf("%f,%f in chord_len\n",a,b);*/
rad=fabs(b-a);
if ( rad > 180) rad = 360-rad;
rad = rad*pi/180;
x=sqrt(2.0)*R*sqrt(1.0-cos(rad));
return x;
}
double arc_len(double a,double b)
{
double x,rad;
rad=fabs(b-a);
if ( rad > 180) rad = 360-rad;
x=R*rad*pi/180;
return x;
}
int main()
{
double a,b;
printf("请输入两个城市的经度（以空格隔开.东经为正,西经为负.）:\n");
scanf("%lf %lf",&a,&b);
printf("%lf,%lf\n",a,b);
printf("两个城市的直线距离为:%f\n",chord_len(a,b));
printf("两个城市的球面距离为:%f\n",arc_len(a,b));
return 0;
}